Truck-mounted trench excavating machine



July 17, 1962 R. E. BALKHEIMER TRUCK-MOUNTED TRENCH EXCAVATING MACHINEFiled Feb. 13, 1959 7 Sheets-Sheet l IN VEN TOR l P" i es@ vl July 17,1962 R. E. BALKHEIMER 3,044,194

TRUCK-MOUNTED 'FRENCH EXCAVATING MACHINE Filed Feb. 13. 1959 7Sheets-Sheet 2 Fig,.2 n f lN-VENTOR July 17, 1962 R. E. BALKHEIMER3,044,194

TRUCK-MOUNTED TRENCH EXCAVATING MACHINE Filed Feb. 13, 1959 7Sheets-Sheet 3 EVENTOR Zim w @74N July 17, 1962 R. E. BALKHEIMERTRUCK-MOUNTED TRENCH EXCAVATING MACHINE '.7 Sheets-Sheet 4 Filed Feb.13. 1959 fad July 17, 1962 R. E. BALKHEIMER TRUCK-MOUNTED TRENCHEXCAVATING MACHINE 7 Sheets-Sheet 5 Filed Feb. 13. 1959 /N VEN TOR July17, 1962 R. E. BALKHEIMER 3,044,194

TRUCK-MOUNTED TRENCH EXCAVATING MACHINE Filed Feb. l5. 1959 7Sheets-Sheet 6 E /NVENTOR Ygzzw( w37@ July 17, 1962 R. E. BALKHEIMER3,044,194

TRUCK-MOUNTED TRENCH v EXCAVATING MACHINE Filed Feb. 15. 1959 7Sheets-Sheet 7 Fig. a

E l VENTOR United States Patent O 3,044,194 TRUCK-MUNTED TRENCHEXCAVATING MACHINE Richard Eugen Balkheimer, Neu Ulm-Oteuhausen,Germany, assignor to Gebruder Eberhardt, Ulm (Danube), Germany, a Germanfirm Filed Feb. 13, 1959, Ser. No. 793,118 Claims priority, applicationGermany Feb. 19, 1958 19 Claims. (Cl. 37-86) The present inventionrelates to a trench excavating machine.

Prior to this invention there have been machines of this kind which werecombined with a tractor so as to form a unit. These known machinesconsist of a chassis with a boom which is adapted to be raised andlowered, and on which-an endless trenching chain or belt provided withblades or teeth is movable in one direction on driving and supportingwheels. These prior machines, together wi-th their boom, may be tiltedabout -their longitudinal and transverse axes so that the depthadjustment and the lateral inclination of the boom and trenching chainrelative to the tractor may be varied. Thus a trench with a uniform,level bot-tom and either with or without an incline and with verticalWalls may be excavated. In order 4to prevent Ithe elevation and l-ateralinclination of the boom from being eifected by the position of themachine, which has to follow the uneven surface and the slopes of theground, the operator of one of these prior excavating machines isrequired to adjust the position of the trench excavating machine and ofthe boom continuously so that the boom with the trenching chain thereonwill no-t vary from the required elevation and lateral perpendicularposition. This machine is controlled -by a manual operation of hydraulicor electric means, either according to the whim of the operator or bymean-s of `an optical pendulum sight which permits the position of themachine and boom to be adjusted in visual alignment with grade stakes orthe like which have been previously erected alongside the intendedtrench. The accurate formation of the trench therefore depends entirelyupon the adroitness and :attentiveness of the operator |who may eithersit on the machine or walk along its side. I-n some of the knownmachines, the boom, together with the excavating chain, is disposedbetween the tracks of the machine, while in other-s it is disposedlaterally of the tracks. Neither type, however, permits any change oradjustment of such arrangement of the boom.

It is an object of the present invention to provide a tinck ortractor-mounted trench excavating machine which is provided with meansfor automatically compensating -for any changes in the position Vof themoving machine relative to the horizontal plane by an adjustment `of theboom with the trenching chain thereon. A further object of the inventionis to provide a trench exca vating machine for digging a trench withvertical walls and a uniform ybottom which may also have a predeterminedincline and which will carry out such an operation automatically andindependently of any particular skill or attentiveness of the operator.Another object of the invention is to provide such a machine whichpermits an adjustment of the boom and trenching chain so that the trenchto be excavated may be either between the tracks fof the machine orlaterally thereof. Another important advantage of the invention consistsin the fact that, since the excavating operation proceeds automatically,the driver of the machine may concentrate his attention entirely uponthe proper steering of the tractor along a prescribed cource which alsodetermines the course of the trench to be dug and which may be eitherstraight or curved.

4and vertical walls.

Still another object of the present invention is to provide a .trenchexcavating machine in which the trenching chain is protected from beingoverloaded when meeting solid rock or other -obstacles in the soil, andwhich is adapted to overcome such obstacles. The machine according tothe invention is further ladapted to refill and level the trenchespreviously excavated thereby.

These and fur-ther objects, features, and advantages of the presentinvention will become more apparent from the following detaileddescription thereof, particularly when read with reference to theaccompanying drawings, in which- -FIGURE l shows a perspective side Viewofthe trench excavating machine according to the invention together witha pipe laying trough and a guide line stretched out alongside theintended course of the trench;

FIGURE 2 shows a perspective rear view of the machine;

FIGURE 3 rshows a diagrammatic side view of the rear part of the machinewith the trenching chain and control mechanism thereon;

FIGURE 4 shows a diagrammatic rear view of the machine;

FIGURE 5 shows a cross section Itaken along line V--V of FIGURE 4;

FIGURE 6 `shows a perspective view of a part of the machine ywith amechanism for controlling the operation of the boom in the event of anoverload upon the trenching chain; l

FIGURE 7 shows a perspective view of an upright -bracket for supportingthe hydraulic means for adjusting the boom and the trenching chain;

FIGURE 8 is a diagrammatic illustration partly in perspective of theautomatic elevation or depth control unit for ythe boom; while FIGURE 9isa diagrammatic illustration, partly in perspective, of the controlunit for adjusting the vertical position of the boom and trenchingchain.

Referring to the drawings, a tractor which preferably runs on fulltracks carries a boom 2 which is mounted on the rear end of the tractorand is provided with an endless trenching chain 3. Boom 2 is secured toa strong crossbar 6 forming a tubular shaft which is rotatably mountedon or within two bearings 4 and 5 and in which a drive shaft 7 isrotatably mounted which carries near one end a sprocket wheel 8 fordriving the trenching chain 3 and on the other end a bevel gear 9 which,as shown in FIGURE 5, is in mesh with a bevel gear 10 which is driven bythe engine of tractor 1 through a shaft 11. The chassis 12 of thetractor carries a bearing bracket 13 for supporting a trunnion 113 onthe gear housing 14 of bevel gears 9 and 10.' Shaft 11 of the drivenbevel gear 10 exten-ds through trunnion 113, thus permitting the gearhousing to be pivoted about the longitudinal axis of the trunnion.Bearing 4 is secured to the tubular shaft 6l. At the other side ofchassis 12., a substantially upright supporting bracket 15 is mountedwhich, as shown particularly iny FIGURES 2 and 7, is provided with anarcuate guideway 16 with a center of curvature coinciding with the axisof shaft 11. A guide plate 17 is slidable along guideway 16 and securedto the bearing 5 of tubular shaft 6. This tubular shaft 6 consists ofseveral parts which are secured to each other by flanges 18 so that,when the flanges are disconnected, the individual parts of shaft 6 maybe removed and replaced by shorter or longer parts. The outer part ofshaft 6 carrying sprocket wheel 8 and boom 2 with in FIGURE 4 indot-and-dash lines. The trenching chain 3 may therefore be mountedeither between the tracks of the tractor or at one side thereof. Shaft 7which is driven by the tractor engine through shaft 11 and extendsthrough the tubular shaft 6 for driving the trenching chain 3 throughsprocket wheel 8 may likewise be rexchanged for a longeror shorter shaftin accordance with the length of tubular shaft 6. Boom 2, however, whichforms an elongated supporting frame, is not adjustable in length. Asidefrom the driven sprocket wheel 8, boom 2 also has a sprocket wheel 20rotatably mounted at its lower end for supporting the trenching chain.The framelike boom 2 is rigidly secured to the tubular shaft 6 so that,when the latter is turned about its axis, boom 2 with trenching chain 3-thereon will be pivoted about the axis of shaft 6 permitting the workingdepth ofthe boom and chain to be adjusted. Shaft 7 further carries asprocket wheel 21 for driving preliminary feed screw 24 through a chain22 and a sprocket wheel 23. This feed screw 24 is'mounted on a shorterboom 2S which is pivotably suspended on tubular shaft 6 and drawn towardthe rear by a spring 27, as shown in FIGURE l. Feed screw 24 divides theexcavated soil which collects immediately in front of chain 3 and passesit to one or two other feed screws 26 which then convey the soil eithertoward one or both sides and pile and pack it together into banksorparapets D, as shown in FIGURE 2. Feed screws 26 are removably securedto a shaft 28 which is mounted on boom 2 and they are driven by thelower Stringer 3i? of trenching chain 3 through sprocket wheels 29, asshown in FIGURE 3. Feed screws 26 may be mounted either on one or bothsides of shaft 2S.

By means of brackets 32 boom 2 further carries a supporting rail 31 onthe lower end of which a scraper blade 33 is mounted. This scraper 33 isslidably adjustable on rail 31 by a bolt 34 extending through alongitudinal slot so as always to rest on the trench bottom S regardlessof the, inclination of boom 2. It is also connected to boom 2 so as tobe easily exchanged for another blade.

The back of supporting rail 31 carries straps or brack- V ets 35supporting a chute 36 through which, for example, short drainage pipesor other objects which are to be laid into the trench may be passedtoward the bottom thereof. Brackets 35 for chute 36 may be designed inthe form of arms which may be pivotably connected to rail 31 and chute36 so as to permit the chute to be inclined to different angles relativeto boom 2.V Thus the chute may always be maintained at substantially thesame inclination relative to the horizontal plane even though the boomchanges its inclination. This is advisable to insure a proper sliding ofthe pipe sections along the chute'into the trench.

The rotatable tubular shaft 6 further carries a sprocket wheel 37 with achain 33 thereon, as shown in FIGURES 3 and 6, the ends of which areconnected to piston rods 39 and 40, the pistons of which are slidable inhydraulic cylinders 41 and 42, respectively. These cylinders are mountedin a box-shaped bracket 43 with arms 44 so as to be loosely butnon-adjustably connected thereto. Arms 44 are secured to an angularbracket 45 in which a plate 46 and a pair of straps 47 are secured andbetween which a roller 48 is rotatably mounted. -A second roller 49 ismounted between arms 44 at a certain distance underneath roller 4S. Onthe upper arm of bracket 45 a rod 50 is mounted by means of a nut 51.Rod 50 extends through the inside of the bracket and carries acompression spring 52, one end of which rests on the upper arm ofbracket 45 while the lower end presses plate 46 with roller 48 thereonin the downward direction. Interposed between -rollers 48 and 49 is thecrossarm of a yokeshaped bracket 53 which is pivotably secured on 'atransverse shaft 54 which is mounted on a part of chassis 12 of thetractor. At one side of the box-shaped bracket 43 and between cylinders41 and' 42 a pair of arms 5S are secured which terminate at their outerend in bearings 56 for supporting the tubular shaft 6.

Supporting bracket 15 on chassis 12 of the tractor contains a hydrauliccylinder 58 which is pivotably connected thereto at its lower end bymeans of a bearing 57 as shown in FIGURE '7. Cylinder 58 contains apiston which is acted upon by oil pressure at both sides and carries apiston rod 59 which is pivotably connected to guide plate 17 which, inturn, is secured to bearing 5. By means of piston rod 59 it is possibleto pivot the tubular shaft 6 together with boom'2 and gear housing Y14relative to tractor 1 about the axis of shaft 11 and approximatelywithin the limits deiined by an angle as indicated in FIGURE 4 by thedot-and-dash lines a and band the two-way arrow B.

Supporting rail 31 further carries on its upper side a bracket 60 onwhich a rod 62 is pivotally mounted so as to be adjustable by means of aturnbuckle 61 or the like. The upper end of rod 62 has a control switch64 rigidly connected thereto, in which a feeler rod 63 is mounted so asto be pivotable about a horizontal axis in a vertical direction. Asshown in FIGURE 8, control switch 64 consists of a housing 65 ofelectrically nonconductive material, the opposite side walls of whichpivotably support an armature to one end of which the feeler rod 63 isrigidly secured, lbut so as to be insulated therefrom, while the otherend carries a Contact arm 66 which, when feeler rod 63 oscillates, alsooscillates between a pair of contacts 67 and 68. Contact arm 66 iselectrically connected by a conductor 70 to one terminal of a source ofcurrent 69, the other terminal of which is connected to ground.

Contact 67 is connected by a conductor 71 to a solenoid 72, whilecontact 68 is connected by a conductor 73 to a solenoid 7'4. The end ofthe winding of each solenoid 72 and 74 is connected to ground so that,when contact arm 66 engages with' one or the other contact 67 or 68, therespective solenoid 72 or 74 will be energized. This solenoid will thenattract a plunger 75 of a servo control valve 76 which is operated byoil pressure, whereby the main control valves 77 =for operating thehydraulic cylinders 41 and 42 as indicated in FIGURE 6 will becontrolled. These control valves 77 then pass oil under pressure from anoil pressure tank, not shown, through conduits 7S and 79 to the rear endof cylinders 41 and 42, respectively, while the front ends of thesecylinders are connected to each other lby a conduit 80 which is alsoconnected to a compensating conduit 81 which, through a check valve 82is directly connected to the oil pressure tank. The mechanism of themain control valves 77 is not specilically illustrated in the drawingssince it is of a design which is generally known in the art of hydrauliccontrols. These control valves 77 may also be manually controlled bycontrol levers 102 which are disposed within the reach of the driver.

Alongside of the trench to be excavated and parallel thereto a pluralityof guide stakes 83 are to be erected on which adjustable brackets 84 aresecured for supporting a tightly stretched guide line 85 in the form ofa steel wire or cable, the ends of which are securely anchored to theground.

The operation of the automatic elevation or depth control of the boomand trenching chain is as follows:

The guide wire 85 is stretched out parallel to the desired trench bottomS regardless of the contours of the surface of the ground. After themachine has been put into operation and the trenching chain 3 on boom 2has penetrated into the soil to the desired depth of the trench bottom,feeler rod 63 will engage loosely with guide line 85, and Contact arm 66will be positioned between cont-acts 67 and 68 without engaging eitherone thereof. At the beginning of the work, the control 'may be carriedout either by a manual operation of a control valve or automatically -bycontrol switches 64- and 8S which will be subsequently described. Ifduring the movement of the tractor the same passes over uneven groundand the boom carrying the trenching chain which is rigidly connected tothe tractor is either raised or lowered accordingly so that the lowerend of the chain either rises above the level of the intended trenchbottom or penetrates to -a greater depth, feeler rod 63 will pivot aboutits bearing in switch housing 65 so that contact arm 66 will engageeither contact 67 or 68. If it engages, for example, contact 68, thecurrent will ow through solenoid 74 which attracts valve plunger 75,thereby allowing the oil to flow from the pressure tank to the maincontrol valve 77 which, in turn, opens the pressure line 79 so that theoil can flow into the rear end of cylinder 42. Thereby .the piston incylinder 42 will be forced toward the front, and the oil then expelledfrom the front part of cylinder v42 will ow through the connectingconduit 80 to the front part of cylinder 42. whereby the piston onpiston rod 39 will be forced toward the rear. Chain 38 will then turnsprocket wheel 37 and tubular shaft 6 thereon in a direction shown bythe arrow C in FIGURE 6 until the lower end of the boom with thetrenching chain 3 thereon again reaches the level which is determined byguide wire 85. 'Because of this movement, switch 64 will also beelevated so that contact arm 66 will again return to its centralposition. Since the solenoid circuit will then be interrupted, valveplunger 75 will return to its neutral position whereby the main controlvalve 77 will be closed and the supply of oil to the hydraulic cylinder42 will be interrupted. lf the tractor runs over a rise in the groundand the boom is lifted accordingly above the intended level S of thetrench bottom, the control operation will be similar as above described,but will proceed in the opposite manner. As soon as the pressureconduits 78 and 79 are shut olf -by the main control valve 77 or bothconduits are subjected to the oil pressure in the pressure tank, thepressure circuit together with arms 5'5, shaft 6, and boom 2 will formya rigid unit with tractor 1.

In order to compensate `for lateral deviations of boom 2 and trenchingchain 3 from the perpendicular plane, a control switch 88 is provided,as shown in FIGURES l, 6, and 9, which is mounted on a bracket 87 which,in turn, may be secured to bearing 5 of the tubular shaft 6 or tobracket on bracket 43. Switch 88 is similar to switch 64 and comprises ahousing 89 o-f nonconductive material with two contacts 90 and 91 on itsopposite walls and a contact arm 92 pivotally suspended in the housingwith its free end disposed between contacts 90 and 91, and a pendulum 93secured to the lower end of the contact arm, but insulated therefrom.Switch 88 is mounted so that pendulum 93 is capable of swinging in adirection transverse to the tractor. A connecting terminal '94 oncontact arm 92 is connected by a conductor 99 to one terminal of abattery 69, the other terminal of which is connected to ground. Switch88 is operatively associated with ya servo control valve 101 similar tovalve 76 shown in FIGURE 8 and provided with a control plunger 100 whichis adapted to move back and forth between solenoids 96 `and 98, one ofwhich is connected by a conductor 95 to switch contact 90, while theother is connected by a conductor 97 to switch contact 91. The ends ofthe windings of solenoids 96 and 98 are likewise connected to ground.Servo control valve 101 controls the operation of a main control valve102, as indicated in FIGURE 6. The pressure conduits 103 and 104 whichare controlled lby valve 102 are connected to the two ends of thehydraulic cylinder 58, as shown in FIGURE 7, the piston rod 59 of whichis connected through guide plate 17 to the bearing 5 of tubular shaft 6,as shown particularly in FIGURE 2.

As long as the tubular shaft 6 with drive shaft 7 therein is disposed ina horizontal position, contact arm 92 will not engage with either-contact or 91. If the tractor drives over uneven ground or along theside of a hill, shaft 6 will be laterally inclined. Since the pendulum93 always hangs perpendicular, one 4of the contacts 90 or 91 will engagewith contact arm 92 whereby one of the solenoids 96 or 98 will beenergized and will adjust the control plunger soi-that oil underpressure will be passed either to the upper or lower end of hydrauliccylinder 58. The piston on piston rod 59 will then shift in cylinder 58in one or the other direction and thereby return shaft 6 to thehorizontal position. Boom 2 with trenching chain 3 thereon will t-husalways be maintained in an exactly perpendicular position even thoughthe tractor might be laterally inclined by driving over uneven ground.

The two types of corrections of the boom at a change of the elevation orof the lateral inclination of the tractor cooperate with each other sothat the correct position of the boom `and trenching chain will alwaysIbe insured.

The present invention provides a third type of control of the boom inthe event that the trenching chain 3 meets an obstacle X, as indicatedin FIGURE 6, which resists the action of the `chain teeth so that thechain will tend to climb up on such obstacle. This will result in -adownward twist in the rigid unit formed of boom 2, trenching chain 3,tubular shaft 6, sprocket wheel 37, chain 38, piston rods 39 and 40,cylinders 41 and 42, and the boxshaped bracket 43 with arms 55. Thisdownward pressure also tends to pull bracket 45 downwardly. This pull isat first opposed by spring 52 which is supported through plate 46 androller 48 on bracket 53. As soon as the spring pressure is overcome bythe increasing resistance of trenching chain 3 on the obstacle whichtends to pivot .the boom upwardly and thereby to turn the tubular shaft6,

bracket 45 and an arm 105 thereon will be lowered so that the latterwill press upon a lever 106 which depresses a control button 111 on themain control valve 77. Control valve 77 is thereby actuated to allow oilunder pressure to flow to cylinder 42 whereby chain 38 will turn shaft 6together with boom 2 4and trenching chain 3 in the clock-wise direction,'as indicated by arrow C. As soon as the obstacle X has .been overcome,the pressure upon bracket 45 will decrease, spring 52 will again liftbracket 45 so that lever 106 will release control button 111, and the owIof oil to cylinder 42 will again be interrupted. Such actuation of thernain control valve 77 also autolmatically interrupts the electricconnection leading to control switch 64, as shown in FIGURE 4, so thatthe closing of switch 64 by an engagement of contact anni 66 withcontact 67 caused by the raising of boom 2 will not have any elfect. Assoon as bracket 45 is again lifted because of a decrease of the pressureon boom 2, the circuit through switch 64 and contact 67 will again -beclosed and boom 2 will again move to the normal depth until feeler rod63 engages with guide wire S5 so that contact 67 will be opened. Thetrenching chain will therefore be able to overcome any obstacle which itcannot dislodge without danger of any damage thereto. If necessary, theoperator of the lmachine may also carry out the dilerent controloperations by hand yby means of the control levers 102.

The tractor -is further provided'at its front end with a dozer orleveling plate 107 which is mounted at both sides of the tractor bymeans of arms 108 which are pivotable about the axis of shaft 54. Twocylinders 109 with pistons therein on piston rods 110 are provided forIr-aising and lowering the dozer plate 107. The flow of oil to thesecylinders may be controlled vby one of the hand levers 102 which :aremounted on the tractor within the reach of the driver. Although such anarrangement is known as such,

it is of special importance in the trench excavating ma-V chineaccording to the invention since it permits the same machine also to beused for leveling the trench by pushing the excavated soil from theparapets D back into the trench.

Although the boom and trenching chain have above been described 'asbeing driven by hydraulic means, they may Yalso be driven byelectromotive means which may be controlled in a similar manner.

Although my invention has been illustrated and described with referencetothe preferred embodiments thereof, I wish to have it understood thatit is in no way limited to the detailsv of such embodiments, but iscapable of numerous modifications within the scope of the appendedclaims.

Having thus fully disclosed @my invention, what I claim 1. Atruck-mounted trench excavating machine comprising a chassis adapted tomove along the ground, a boom pivotably mounted on said chassis `at oneend thereof, an endless trenching chain mounted on said boom forcontinuous movement along the same, driving means for pivoting said.boom to a given position independently of the vertical and horizontalpositions of said chassis about an axis extending longitudinally of saidchassis and also about lan axis extending transversely thereto, saiddriving means capable of retaining the boom in said position during4position changes of said chassis, and driving means for driving saidchain along said boom.

2. A trench excavating machine as deiined in Vclaim l, furthercomprising a scraper blade removably connected to the free end ofV saidboom and slidably adjustable thereon in the longitudinal direction ofsmd boom for scraping the bottom of the trench.

3. A truck-mounted trench excavating machine comprising a chassisadapted to move along the ground, a transverse member pivotably mountedon said chassis near one end thereof, said member extending transverseto the longitudinal axis of said chassis, a longitudinal boom memberextending at an angle to said transverse member and rigidly securedthereto near the end remote from said chassis, means for pivoting saidtransverse member and said boom member relative to said chassis to agiven position about said longitudinal axis and for also pivoting saidboom member relative to said chassis about the axis of said transversemember, an endless trenching chain mounted on said longitudinal boommember for continuous movement along the same, driving means forpivoting said transverse member and said boom member about each'of saidtwo axes independently of each other, said driving means for pivotingcapable of retaining the boom in said position during movement of saidchassis, and driving means for driving said chain along saidlongitudinal boom member.

4. A trench excavating machine as deiined in claim 3, f

wherein said means for pivotably mounting said transverse membercomprise a trunnion rotatably mounted on said chassis about saidlongitudinal axis, and bearing means on said trunnion for rotatablymounting said transverse member about its own axis transverse to saidlongitudinal axis.

5. A trench excavating machine as defined in claim 3, wherein said meansfor pivotably mounting said transverse member comprise a trunnionmounted on said chassis and having a central aperture and an axiscoincid- -ingY with said longitudinal axis, a gear housing rotatablymounted on said trunnion about said axis, said transverse membercomprising a tubular shaft, said driving means for driving said chaincomprising power driving means mounted on said chassis, a drive shaftextending along said longitudinal axis from said power means into saidgear housing, a driven shaft extending into said gear housing androtatably through Vsaid tubular shaft, bearing means on said gearhousing for rotatably supporting said two shafts at an angle to eachother, meshing bevel gears on 'one end of each of said shafts withinsaid gear housing,

and power transmitting means near the other end of said driven shaft fordriving said trenching chain.

6. A trench excavating -machine as dened in claim 5, wherein saidtubular shaft is rotatably mounted on said driven shaft, said tubularshaft beingri'gidly secured near said other end of said driven shaft tosaid longitudinal boom member, said driving means for pivoting said boomcomprising driving means for pivoting said tubular shaft 5 and saidlongitudinal boom member thereon about said driven shaft.

7. A trench excavating machine as delined in claim 6, wherein saiddriving means for pivoting said boom further comprise driving meansseparate from said last-mentioned driving means for pivoting saidtubular and driven shaft and said longitudinal boom member thereon aboutsaid longitudinal axis by a planetary movement of said bevel gears abouteach other.

8. A trench excavating machine as defined in claim 6 wherein saiddriving means for pivoting said tubular shaft about said driven shaftcomprise hydraulic means including a pair of hydraulic cylindersconnected to said chassis and having pistons slidable therein, a pistonrod on each piston, a sprocket wheel mounted on said tubular shaft, anda chain on said sprocket wheel and connected at each end to one of saidpiston rods, and at least one bearing arm having means near one endthereof for rotatably supporting said tubular shaft and being secured atthe other end to said-chassis and disposed between said hydrauliccylinders.

9. A trench excavatingV machine as defined in claim 8, wherein saidhydraulic means comprising a source of pressure, valve control meansconnected to said source, pressure conduits connecting said valvecontrol means to one end of each of said hydraulic cylinders, a conduitconnecting the other end of each of said cylinders to each other, and acompensating conduit connected to said connecting conduit for movingsaid pistons in said cylinders in response to each other and in oppositedirections of each other and for locking them in the adjusted positions,and for locking said tubular shaft against a pivotal movement about itsown axis caused by an excessive load upon said trenching chain.

l0. A trench excavating machine as defined in claim l, furthercomprising control means for cont-rolling the opera-tion `of saiddriving means for pivoting said boom and comprising -a guide -lineytightly stretched alongside the intended course of the trench to beexcavated and at a certain height from the bottom of the intendedtrench, an electric switch mounted on said boom, a` feeler arm pivotablymounted `at yone end o-n said switch about a substantially horizontallaxis and normally adapted to remain in engagement near its other endwith said guide line, and electric control means electrically connectedto said switch and to said driving means for operating the latter inaccordance with any pivotal movement of said feeler arm in eitherdirection.

l1. A trench excavating machine as dened in claim 9, wherein said valvecon-troll means comprise at least one solenoid-'operated valve, andcontrol means for controlling the operation of said valve comprising aguide l-ine tightly stretched alongside the intended course of thetrench to be excavated and at a certain height from the bottom of theintended trench, an electric switch mounted on said longitudinal boommember, a feeler arm. pivotlably mounted at one end on said switch abouta subst-antially horizontal axis and normally adapted to remain inengagement near its other end with said guide Iline, and means forelectrically connecting said switch with said valve for operating thesame in accordance with any pivotal movement of said fceler arm ineither direction.

l2. A trench excavating machine as defined in claim 9, furthercomprising means for connecting said cylinders to said chassis, saidmeans comprising a supporting member pivotably mounted on said chassis,a second supporting member carrying said cylinders mounted on said lirstsupporting member so as to be slidable vertically the-reto, and a thirdsupporting member carrying a spring interposed between said iirst andsecond supporting members, and a member connected to said lthirdsupporting member 9 and adapted to act upon said valve control means tooperate said pistons in said cylinders to pivot said tubular shaft aboutits own axis and thus to pivot said longitudinal boom member and saidtrenching chain thereon in an upward` direction.

13. A trench excavating machine as dened in claim 9, further comprisingmeans for -selectively controlling said valve control means by manualand automatic operations.

14. A trench excavating machine as defined in claim 1, wherein saidmeans for pivoting said boo-m about said longitudinal axis comprise asubstantially upright supporting `member mounted on said chassis andspaced from said longitudinal axis, a bea-ring member for supportingsaid boom [and spaced from said longitudinal axis, hydraulic meansincluding a `hydraulic cylinder having a piston slidably mounted in saidcylinder and a piston rod on said piston, said cylinder and said pistonrod each having one outer end portion, one .of said end portions beingsecured to said supporting member and the other end portion beingslidably guided by said supporting member and connected to said bearingmember, a solenoid-operated valve, pressure conduits connecting saidvalve with the opposite ends of said cylinder, and a pendulum-operatedelectric switch mounted on said bearing member so that the pendulumthereof is pivotable about an axis substantially parallel to saidlongitudinal axis and electrically connected with lsaid valve foroperating the same in accordance with the pivotal position of said boomabout said longitudinal axis, so that said piston and piston rod will beadjusted to act upon said bearing member to maintain said trenchingchain in a lateral direction of said chassis in a predetermined positionrelative to a horizontal plane.

15. A trench excavating machine as defined in claim 1, furthercomprising a dozer plate at the other end of said chassis for levelingthe soil excavated from said trench and refilling said trench.

16. A trench excavating machine as defined in claim 1, furthercomprising a chutelike member mounted on said 10 boom for slidingobjects into said trench to be laid therein.

17. A trench excavating machine as defined in claim 1, funthercomprising a feed screw mounted on said chassis in advance of saidtrenching chain for dividing the soil excavated lrom said trench andconveying it at least toward one side of said trench, a second feedscrew behind said first feed screw for forming said excavated soil intoa parapet at least at one side of said trench, and means for drivingsaid feed screws.

18. A trench excavating machine as dened in claim 3, wherein saidtransverse member is of an adjustable length so as to permit the boomand t-renching chain thereon to be selectively operated between thetracks of said chassis and at different `distances laterally therefrom.

19. A trench excavating 4machine as dened in claim 3 wherein saidtransverse member comprises a tubular shaft secured at one end to saidlongitudinal boom. member, and la drive shaft for driving said trenchingchain extending .through said tubular shaft, at least said tubular shaftconsisting of a plurality of sections and means for removably securingsaid sections to each other so as to permit the length of said shaft tobe varied so that the longitudinal boom member Iand the trenching chainthereon may be selectively operated between the tracks of said chassisand at least at one certain distance laterally thereof.

References Cited in the le of this patent UNITED STATES PATENTS1,501,621 Ronning et al. July 15, 1924 2,065,809 Joy Dec. 29, 19362,681,517 Schmidt June 22, 1954 2,710,466 Chartier June 14, 19552,747,292 Dumler May 29, 1956 2,751,698 Brown June 26, 1956 2,787,844Schmidt Apr. 9, 1957 2,817,911 Owen et al. Dec. 31, 1957 2,873,541Eliason Feb. 17, 1957

